1. Field of the Invention
The present invention generally relates to a network system composed of a plurality of local-area networks (LANs) connected by a plurality of routing nodes and in particular to a routing address management techniques using an address learning table when a new host is connected to a LAN or a host moves from a LAN to another LAN within the network.
2. Description of the Related Art
A routing node connecting a LAN with another LAN is allowed to recognize a host connected to a LAN by monitoring the source address (SA) of data frame flowing on each of the LANS. More specifically a routing node is provided with an address, learning table containing address information for each host. Therefore, in the case where a new host is connected to a LAN or an existing host is moved to another LAN, the routing node can recognize the host by referring to the address learning table. Each routing node can manage the address information of the hosts using the address learning table. Further, by the routing nodes referring to the address learning tables thereof, efficient data frame transfer can be achieved in the network.
It is necessary to update such an address learning table when a new host is connected to a LAN or an existing host is moved to another LAN. There have been proposed several methods for automatically updating the address learning table.
According to a first conventional example, a bridge devica connecting a plurality of LANs is provided with an address learning table. In the case where an existing terminal moves from a first LAN to a second LAN, the bridge device searches the address learning table for the source address of a data frame received from the terminal. If the same address is found, the registered address information is deleted from the address learning table and the new address information indicating that the terminal is connected to the second LAN is registered onto the address learning table. In this way, the address learning table is updated when a terminal moves from a LAN to another LAN. Such a first conventional method has been disclosed in Japanese Patent Unexamined Publication No. 4-154335.
According to a second conventional example, a bridge device is provided with an address learning table and a server stores a duplication of the address information of the address learning table at regular intervals. The server uses the duplication to check the location of a mobile host. In the case where the server receives no response to the check operation from the mobile host, the server determines that the mobile host has moved to anther LAN and instructs the bridge device to delete the address information for the mobile host from the address learning table. Thereafter, when receiving a response to a check operation from the mobile host, the new address information of the mobile host is registered onto the address learning table. Such a second conventional method has been disclosed in Japanese Patent Unexamined Publication No. 10-23056.
However, the first conventional method does not provide a means for informing other bridge devices of the update of the address devices. According to the second conventional method, it is necessary for the server to instruct the bridge device to perform a deletion operation and, if receiving the response then to perform a registration operation. Therefore, there are cases where the status of the address learning table is different from one bridge device to another. Further, the two operation steps cause the processing time to become longer.
An object of the present invention is to provide a routing address management method and system which can update the address learning table of each routing node in a short time.
Another object of the present invention is to provide a routing address management method and system which can reduce the number of control messages, resulting in reduced traffic in the network system.
Still another object of the present invention is to provide a routing address management method and system which can reduce the burden of a routing server in the network system.
According to the present invention, in a network system including a plurality of hosts and a plurality of networks which are connected by a plurality of routing nodes each having an address learning table storing address information for each of the hosts, wherein each of the hosts can be connected to one of the networks, a routing address management method includes the following steps:
at a routing node, monitoring a network connected to the routing node to determine whether a new host is connected to the network; when it is determined that a new host is connected to the network, updating an address learning table thereof depending on new address information of the new host; producing a control message including the new address information after the address learning table has been updated; and
at the routing nodes other than the routing node, updating address learning tables thereof depending on the new address information included in the control message.
According to another aspect of the present invention, in a network system including a routing server, a plurality of hosts, and a plurality of networks, a routing node monitors a network connected to the routing node to determine whether a new host is connected to the network. When it is determined that the new host is connected to the network, an address learning table thereof is updated depending on new address information of the new host. After the address learning table has been updated, an update notifying message including the new address information is sent to the routing server. The routing server, in response to the update notifying message, sends an update request message to the routing nodes other than the routing node, the update request message including the new address information of the new host. The routing nodes other than the routing node updates address learning tables thereof depending on the new address information included in the update request message.
Preferably each of the routing nodes other the routing node sends an update completion message to the routing server when an address learning table has been updated.
The routing server preferably starts a timer set for a predetermined time period when the update request message is sent and determines whether the update completion message is received from each of the routing nodes other than the routing node. The update request completion message is not received until the predetermined time period has elapsed. The timer is stopped when the update completion message has been received from each of the routing nodes other than the routing node.
According to a still another aspect of the present invention, in a network system including a plurality of hosts and a plurality of networks which are connected by a plurality of routing nodes each having an address learning table storing address information for each of the hosts, wherein each of the hosts can be connected to one of the networks, a routing node monitors a network connected to the routing node to determine whether a new host is connected to the network. When it is determined that the new host is connected to the network, an address learning table thereof is updated depending on new address information of the new host. Then an update request message is sent to the routing nodes other than the routing node after the address learning table has been updated. The update request message includes the new address information of the new host. The routing nodes other than the routing node updates address learning tables thereof depending on the new address information included in the update request message.
As described above, in each of the routing nodes, deletion of old address information and registration of new address information are both performed at a time in the address learning table thereof, resulting in the reduced time required for updating the address learning table of each routing node and the reduced burden on the routing node or the routing server.
Further, since a single message is used to delete the old registered address information and register the new address information in the address learning table in each routing node, the address information update in each routing node is made reliable and the traffic in the network system can be reduced. Furthermore, the reduced burden on the routing server can be achieved.